Mobile phones, personal digital assistants (PDAs), digital cameras, MP3 players, and other portable electronic devices utilize LEDs for background illumination. FIG. 1 is a cross-sectional diagram of a portion of a conventional indium-gallium nitride (“InGaN”) LED 10. As shown in FIG. 1A, the LED 10 includes a substrate 12, an optional buffer material 13 (e.g., aluminum nitride), an N-type gallium nitride (“GaN”) material 14, an InGaN material 16 (and/or GaN multiple quantum wells), and a P-type GaN material 18 on top of one another in series. The LED 10 also includes a first contact 20 on the P-type GaN material 18 and a second contact 22 on the N-type GaN material 14.
The LED 10 should be configurable to emit at a wide range of wavelengths. It is believed that the wavelength at which the LED 10 emits is at least partially related to the amount of indium (In) in the InGaN material 16. For example, a larger amount of indium in the InGaN material 16 has been associated with longer emission wavelengths of the LED 10.
One technique for enhancing the incorporation of indium in the InGaN material 16 is to form the GaN/InGaN materials 14, 16, and 18 on nitrogen-polarity surfaces rather than on gallium-polarity surfaces via nitrodizing the substrate 12. However, one operational difficulty of this technique is that the nitrodizing product of the substrate 12 may interfere with subsequent deposition of the GaN/InGaN materials 14, 16, and 18 thereon. Thus, several improvements in forming LED structures on nitrogen-polarity surfaces of substrates may be desirable.